cc: Add experimental --num-raster-threads option.

cc/tile_manager.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/tile_manager.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
+#include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
+#include "base/string_number_conversions.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "cc/platform_color.h"
 #include "cc/rendering_stats.h"
 #include "cc/resource_pool.h"
+#include "cc/switches.h"
 #include "cc/tile.h"
 #include "third_party/skia/include/core/SkDevice.h"
 
 namespace {
 
 void RasterizeTile(cc::PicturePileImpl* picture_pile,
                    uint8_t* mapped_buffer,
                    const gfx::Rect& rect,
                    cc::RenderingStats* stats) {
   TRACE_EVENT0("cc", "RasterizeTile");
   DCHECK(mapped_buffer);
   DCHECK(picture_pile);
   SkBitmap bitmap;
   bitmap.setConfig(SkBitmap::kARGB_8888_Config, rect.width(), rect.height());
   bitmap.setPixels(mapped_buffer);
   SkDevice device(bitmap);
   SkCanvas canvas(&device);
   picture_pile->Raster(&canvas, rect, stats);
 }
 
-const int kMaxRasterThreads = 1;
+const int kMaxRasterThreads = 64;
+const int kDefaultNumberOfRasterThreads = 1;
 
 const char* kRasterThreadNamePrefix = "CompositorRaster";
 
 // Allow two pending raster tasks per thread. This keeps resource usage
 // low while making sure raster threads aren't unnecessarily idle.
 const int kNumPendingRasterTasksPerThread = 2;
 
 }  // namespace
 
 namespace cc {
@@ skipping 10 matching lines @@
   DCHECK(!resource_id);
   DCHECK(!resource_id_is_being_initialized);
 }
 
 TileManager::TileManager(
     TileManagerClient* client, ResourceProvider* resource_provider)
     : client_(client),
       resource_pool_(ResourcePool::Create(resource_provider,
                                           Renderer::ImplPool)),
       manage_tiles_pending_(false),
-      pending_raster_tasks_(0),
-      worker_pool_(new base::SequencedWorkerPool(kMaxRasterThreads,
-                                                 kRasterThreadNamePrefix)) {
+      pending_raster_tasks_(0) {
+  size_t worker_threads = kDefaultNumberOfRasterThreads;
+  if (CommandLine::ForCurrentProcess()->HasSwitch(

[enne (OOO), 2012/12/03 17:47:42]

Given that ubercompositor may want to set properties differently in the future,
I'd really like if new settings could go through a LayerTreeSettings indirection
so that we weren't checking global command line state.

+          cc::switches::kNumRasterThreads)) {
+    std::string num_raster_threads =
+        CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+            cc::switches::kNumRasterThreads);
+    int num_threads;
+    if (base::StringToInt(num_raster_threads, &num_threads) &&
+        num_threads > 0 && num_threads <= kMaxRasterThreads) {
+      worker_threads = num_threads;
+    } else {
+      LOG(WARNING) << "Bad number of raster threads: " << num_raster_threads;
+    }
+  }
+  worker_pool_ = new base::SequencedWorkerPool(worker_threads,
+                                               kRasterThreadNamePrefix);
 }
 
 TileManager::~TileManager() {
   // Reset global state and manage. This should cause
   // our memory usage to drop to zero.
   global_state_ = GlobalStateThatImpactsTilePriority();
   ManageTiles();
   DCHECK(tiles_.size() == 0);
   // This should finish all pending raster tasks and release any
   // uninitialized resources.
@@ skipping 301 matching lines @@
     Tile* tile, ResourceProvider::ResourceId resource_id) {
   ManagedTileState& managed_tile_state = tile->managed_state();
   DCHECK(!managed_tile_state.resource_id);
   managed_tile_state.resource_id = resource_id;
   managed_tile_state.resource_id_is_being_initialized = false;
   // TODO(qinmin): Make this conditional on managed_tile_state.bin == NOW_BIN.
   client_->ScheduleRedraw();
 }
 
 }